<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
<title>Source code</title>
<link rel="stylesheet" type="text/css" href="../../../../../../stylesheet.css" title="Style">
</head>
<body>
<div class="sourceContainer">
<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import java.util.concurrent.Executor;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.util.concurrent.ExecutorService;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.util.concurrent.Future;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.util.concurrent.FutureTask;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.util.concurrent.RejectedExecutionException;<a name="line.23"></a>
<span class="sourceLineNo">024</span><a name="line.24"></a>
<span class="sourceLineNo">025</span>/**<a name="line.25"></a>
<span class="sourceLineNo">026</span> * A {@link Future} that accepts completion listeners.  Each listener has an<a name="line.26"></a>
<span class="sourceLineNo">027</span> * associated executor, and it is invoked using this executor once the future's<a name="line.27"></a>
<span class="sourceLineNo">028</span> * computation is {@linkplain Future#isDone() complete}.  If the computation has<a name="line.28"></a>
<span class="sourceLineNo">029</span> * already completed when the listener is added, the listener will execute<a name="line.29"></a>
<span class="sourceLineNo">030</span> * immediately.<a name="line.30"></a>
<span class="sourceLineNo">031</span> * <a name="line.31"></a>
<span class="sourceLineNo">032</span> * &lt;p&gt;See the Guava User Guide article on &lt;a href=<a name="line.32"></a>
<span class="sourceLineNo">033</span> * "http://code.google.com/p/guava-libraries/wiki/ListenableFutureExplained"&gt;<a name="line.33"></a>
<span class="sourceLineNo">034</span> * {@code ListenableFuture}&lt;/a&gt;.<a name="line.34"></a>
<span class="sourceLineNo">035</span> *<a name="line.35"></a>
<span class="sourceLineNo">036</span> * &lt;h3&gt;Purpose&lt;/h3&gt;<a name="line.36"></a>
<span class="sourceLineNo">037</span> *<a name="line.37"></a>
<span class="sourceLineNo">038</span> * Most commonly, {@code ListenableFuture} is used as an input to another<a name="line.38"></a>
<span class="sourceLineNo">039</span> * derived {@code Future}, as in {@link Futures#allAsList(Iterable)<a name="line.39"></a>
<span class="sourceLineNo">040</span> * Futures.allAsList}. Many such methods are impossible to implement efficiently<a name="line.40"></a>
<span class="sourceLineNo">041</span> * without listener support.<a name="line.41"></a>
<span class="sourceLineNo">042</span> *<a name="line.42"></a>
<span class="sourceLineNo">043</span> * &lt;p&gt;It is possible to call {@link #addListener addListener} directly, but this<a name="line.43"></a>
<span class="sourceLineNo">044</span> * is uncommon because the {@code Runnable} interface does not provide direct<a name="line.44"></a>
<span class="sourceLineNo">045</span> * access to the {@code Future} result. (Users who want such access may prefer<a name="line.45"></a>
<span class="sourceLineNo">046</span> * {@link Futures#addCallback Futures.addCallback}.) Still, direct {@code<a name="line.46"></a>
<span class="sourceLineNo">047</span> * addListener} calls are occasionally useful:&lt;pre&gt;   {@code<a name="line.47"></a>
<span class="sourceLineNo">048</span> *   final String name = ...;<a name="line.48"></a>
<span class="sourceLineNo">049</span> *   inFlight.add(name);<a name="line.49"></a>
<span class="sourceLineNo">050</span> *   ListenableFuture&lt;Result&gt; future = service.query(name);<a name="line.50"></a>
<span class="sourceLineNo">051</span> *   future.addListener(new Runnable() {<a name="line.51"></a>
<span class="sourceLineNo">052</span> *     public void run() {<a name="line.52"></a>
<span class="sourceLineNo">053</span> *       processedCount.incrementAndGet();<a name="line.53"></a>
<span class="sourceLineNo">054</span> *       inFlight.remove(name);<a name="line.54"></a>
<span class="sourceLineNo">055</span> *       lastProcessed.set(name);<a name="line.55"></a>
<span class="sourceLineNo">056</span> *       logger.info("Done with {0}", name);<a name="line.56"></a>
<span class="sourceLineNo">057</span> *     }<a name="line.57"></a>
<span class="sourceLineNo">058</span> *   }, executor);}&lt;/pre&gt;<a name="line.58"></a>
<span class="sourceLineNo">059</span> *<a name="line.59"></a>
<span class="sourceLineNo">060</span> * &lt;h3&gt;How to get an instance&lt;/h3&gt;<a name="line.60"></a>
<span class="sourceLineNo">061</span> *<a name="line.61"></a>
<span class="sourceLineNo">062</span> * Developers are encouraged to return {@code ListenableFuture} from their<a name="line.62"></a>
<span class="sourceLineNo">063</span> * methods so that users can take advantages of the utilities built atop the<a name="line.63"></a>
<span class="sourceLineNo">064</span> * class. The way that they will create {@code ListenableFuture} instances<a name="line.64"></a>
<span class="sourceLineNo">065</span> * depends on how they currently create {@code Future} instances:<a name="line.65"></a>
<span class="sourceLineNo">066</span> * &lt;ul&gt;<a name="line.66"></a>
<span class="sourceLineNo">067</span> * &lt;li&gt;If they are returned from an {@code ExecutorService}, convert that<a name="line.67"></a>
<span class="sourceLineNo">068</span> * service to a {@link ListeningExecutorService}, usually by calling {@link<a name="line.68"></a>
<span class="sourceLineNo">069</span> * MoreExecutors#listeningDecorator(ExecutorService)<a name="line.69"></a>
<span class="sourceLineNo">070</span> * MoreExecutors.listeningDecorator}. (Custom executors may find it more<a name="line.70"></a>
<span class="sourceLineNo">071</span> * convenient to use {@link ListenableFutureTask} directly.)<a name="line.71"></a>
<span class="sourceLineNo">072</span> * &lt;li&gt;If they are manually filled in by a call to {@link FutureTask#set} or a<a name="line.72"></a>
<span class="sourceLineNo">073</span> * similar method, create a {@link SettableFuture} instead. (Users with more<a name="line.73"></a>
<span class="sourceLineNo">074</span> * complex needs may prefer {@link AbstractFuture}.)<a name="line.74"></a>
<span class="sourceLineNo">075</span> * &lt;/ul&gt;<a name="line.75"></a>
<span class="sourceLineNo">076</span> *<a name="line.76"></a>
<span class="sourceLineNo">077</span> * Occasionally, an API will return a plain {@code Future} and it will be<a name="line.77"></a>
<span class="sourceLineNo">078</span> * impossible to change the return type. For this case, we provide a more<a name="line.78"></a>
<span class="sourceLineNo">079</span> * expensive workaround in {@code JdkFutureAdapters}. However, when possible, it<a name="line.79"></a>
<span class="sourceLineNo">080</span> * is more efficient and reliable to create a {@code ListenableFuture} directly.<a name="line.80"></a>
<span class="sourceLineNo">081</span> *<a name="line.81"></a>
<span class="sourceLineNo">082</span> * @author Sven Mawson<a name="line.82"></a>
<span class="sourceLineNo">083</span> * @author Nishant Thakkar<a name="line.83"></a>
<span class="sourceLineNo">084</span> * @since 1.0<a name="line.84"></a>
<span class="sourceLineNo">085</span> */<a name="line.85"></a>
<span class="sourceLineNo">086</span>public interface ListenableFuture&lt;V&gt; extends Future&lt;V&gt; {<a name="line.86"></a>
<span class="sourceLineNo">087</span>  /**<a name="line.87"></a>
<span class="sourceLineNo">088</span>   * Registers a listener to be {@linkplain Executor#execute(Runnable) run} on<a name="line.88"></a>
<span class="sourceLineNo">089</span>   * the given executor.  The listener will run when the {@code Future}'s<a name="line.89"></a>
<span class="sourceLineNo">090</span>   * computation is {@linkplain Future#isDone() complete} or, if the computation<a name="line.90"></a>
<span class="sourceLineNo">091</span>   * is already complete, immediately.<a name="line.91"></a>
<span class="sourceLineNo">092</span>   *<a name="line.92"></a>
<span class="sourceLineNo">093</span>   * &lt;p&gt;There is no guaranteed ordering of execution of listeners, but any<a name="line.93"></a>
<span class="sourceLineNo">094</span>   * listener added through this method is guaranteed to be called once the<a name="line.94"></a>
<span class="sourceLineNo">095</span>   * computation is complete.<a name="line.95"></a>
<span class="sourceLineNo">096</span>   *<a name="line.96"></a>
<span class="sourceLineNo">097</span>   * &lt;p&gt;Exceptions thrown by a listener will be propagated up to the executor.<a name="line.97"></a>
<span class="sourceLineNo">098</span>   * Any exception thrown during {@code Executor.execute} (e.g., a {@code<a name="line.98"></a>
<span class="sourceLineNo">099</span>   * RejectedExecutionException} or an exception thrown by {@linkplain<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * MoreExecutors#sameThreadExecutor inline execution}) will be caught and<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * logged.<a name="line.101"></a>
<span class="sourceLineNo">102</span>   *<a name="line.102"></a>
<span class="sourceLineNo">103</span>   * &lt;p&gt;Note: For fast, lightweight listeners that would be safe to execute in<a name="line.103"></a>
<span class="sourceLineNo">104</span>   * any thread, consider {@link MoreExecutors#sameThreadExecutor}. For heavier<a name="line.104"></a>
<span class="sourceLineNo">105</span>   * listeners, {@code sameThreadExecutor()} carries some caveats.  For<a name="line.105"></a>
<span class="sourceLineNo">106</span>   * example, the listener may run on an unpredictable or undesirable thread:<a name="line.106"></a>
<span class="sourceLineNo">107</span>   *<a name="line.107"></a>
<span class="sourceLineNo">108</span>   * &lt;ul&gt;<a name="line.108"></a>
<span class="sourceLineNo">109</span>   * &lt;li&gt;If the input {@code Future} is done at the time {@code addListener} is<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * called, {@code addListener} will execute the listener inline.<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * &lt;li&gt;If the input {@code Future} is not yet done, {@code addListener} will<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * schedule the listener to be run by the thread that completes the input<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * {@code Future}, which may be an internal system thread such as an RPC<a name="line.113"></a>
<span class="sourceLineNo">114</span>   * network thread.<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * &lt;/ul&gt;<a name="line.115"></a>
<span class="sourceLineNo">116</span>   *<a name="line.116"></a>
<span class="sourceLineNo">117</span>   * Also note that, regardless of which thread executes the listener, all<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * other registered but unexecuted listeners are prevented from running<a name="line.118"></a>
<span class="sourceLineNo">119</span>   * during its execution, even if those listeners are to run in other<a name="line.119"></a>
<span class="sourceLineNo">120</span>   * executors.<a name="line.120"></a>
<span class="sourceLineNo">121</span>   *<a name="line.121"></a>
<span class="sourceLineNo">122</span>   * &lt;p&gt;This is the most general listener interface. For common operations<a name="line.122"></a>
<span class="sourceLineNo">123</span>   * performed using listeners, see {@link<a name="line.123"></a>
<span class="sourceLineNo">124</span>   * com.google.common.util.concurrent.Futures}. For a simplified but general<a name="line.124"></a>
<span class="sourceLineNo">125</span>   * listener interface, see {@link<a name="line.125"></a>
<span class="sourceLineNo">126</span>   * com.google.common.util.concurrent.Futures#addCallback addCallback()}.<a name="line.126"></a>
<span class="sourceLineNo">127</span>   *<a name="line.127"></a>
<span class="sourceLineNo">128</span>   * @param listener the listener to run when the computation is complete<a name="line.128"></a>
<span class="sourceLineNo">129</span>   * @param executor the executor to run the listener in<a name="line.129"></a>
<span class="sourceLineNo">130</span>   * @throws NullPointerException if the executor or listener was null<a name="line.130"></a>
<span class="sourceLineNo">131</span>   * @throws RejectedExecutionException if we tried to execute the listener<a name="line.131"></a>
<span class="sourceLineNo">132</span>   *         immediately but the executor rejected it.<a name="line.132"></a>
<span class="sourceLineNo">133</span>   */<a name="line.133"></a>
<span class="sourceLineNo">134</span>  void addListener(Runnable listener, Executor executor);<a name="line.134"></a>
<span class="sourceLineNo">135</span>}<a name="line.135"></a>




























































</pre>
</div>
</body>
</html>
